The present invention is directed to apparatus for reducing wear in an elbow of a pipe carrying solids in a stream of gas. An example is the coal nozzle inlet elbow leading to a burner in a steam generating furnace. The larger particles of coal impacting on the elbow causes considerable wear, leading to frequent shutdowns to replace the elbow. Attempts to solve the problem include putting a ceramic liner in the elbow, or making the entire elbow of ceramic material. The cost of such an elbow is many times that of a metal elbow, and in addition the ceramic elbow or liner can be easily broken.
Another problem associated with coal fired burners is being able to fire them at low load, while maintaining stable flame conditions, without the need for costly secondary fuel, such as oil or gas. U.S. Pat. No. 4,274,343 discloses a burner capable of such operation. This patent discloses a burner having an upper outlet opening a lower outlet opening, and it relies on separation of the fuel by centrifigal force as it flows through an elbow. Thus the coal-air stream flowing to the upper outlet is dense enough to maintain a stable flame. The present invention is also an improvement on the above patent.